A balloon catheter which is fitted with a balloon at a distal top end portion of the main body of the catheter is provided therein with a heating means. The heating liquid filled in the balloon is heated with the heating means, and the heated balloon is brought into contact with the body tissues, thereby locally cauterizing and consequently treating the body tissues. The balloon is further provided with a thermocouple acting as a thermosensor for detecting the temperature of the heating liquid.
The heating-type balloon catheter device is desired in some cases to be used for cauterizing a considerably wide area of the body tissues with the balloon. To be more specific, for instance, if an abnormal path (an accessory conduction passage) would exist over a passage of electrical signals for moving the heart, it may cause symptoms such as vertigo and sick sensation which are referred to as atrial fibrillation. The atrial fibrillation may further cause the deterioration of cardiac incompetence or constitute a serious cause for brain infarction. In order to cut off the abnormal conduction path formed in the pulmonary vein, an edge portion of the opening of the pulmonary vein opening toward the left ventricle (the pulmonary vein orifice) is desirably cauterized totally, i.e., in an annular fashion.
As described above, in the event where the heating liquid filled in the balloon is heated while sustaining the temperature to be detected with the thermocouple fitted in the balloon to a predetermined temperature in a state in which the balloon is in annular contact with the pulmonary vein as a whole, it has been found that an event may be caused to occur where a state in which the pulmonary vein is cauterized in a peripheral direction may vary to a considerable extent. In other words, it has been found that this event may lead to a state in which a certain portion of the pulmonary vein orifice is over-heated while the other portion thereof is heated to a lesser and insufficient level.
Japanese Patent Application Publication No. 2003-111,848 discloses the technique in which heating liquid filled in the balloon is stirred by utilizing vibration in order to uniform the temperature of the heating liquid in the balloon. More specifically, the device of this type is constructed in such a manner that a vibration imparting device for imparting vibration is connected to the base end portion of a catheter main body and a passage extending from the vibration imparting device to the balloon is filled with the heating liquid so as to transmit the vibration imparted with the vibration imparting device to the heating liquid in the balloon through the heating liquid within the catheter main body.
Some devices for imparting vibration are proposed, which include a device of the type that utilizes a diaphragm drivable reciprocally with a motor or a device of the type that expands or contracts an elastic tube connected to the base end portion of the catheter main body in its radial direction with a member drivable reciprocally.
It is to be noted herein that the balloon having a different size may be used selectively by complying with a variation in the body size of a patient or a site of cauterization or the like. The size of the balloon may be 20φ, 25φ or 30φ for example.
As described above, it has been found that, in the event that the size of the balloon is varied, an undesirable deformation in expansion and shrinkage of the balloon would be caused to occur due to a difference in uniformity of the temperature of the heating liquid in the balloon even if an equivalent or similar level of vibration would be imparted to the vibration imparting device. In other words, in the event that an appropriate level of vibration is set to a smaller-sized balloon, the extent of vibration (e.g., the extent of stirring) may be too small for a larger-sized balloon, thereby resulting in the likelihood that the temperature of the heating liquid within the balloon remains irregular. Conversely, in the event that an appropriate level of vibration is set to a larger-sized balloon, it is too large for a smaller-sized balloon, thereby causing a repetition of expansion and shrinkage of the balloon to a great extent. In other words, problems may likely occur that the balloon is caused to come into contact with the site of cauterization (if the balloon would expands too much), while the balloon is positioned apart from the site of cauterization (if the balloon would shrink too much).